Demand-indicator.



No. 835,484. PATENTED NOV. 6, 1906.

L. WILSON.

DEMAND INDICATUR.

APYPLIOATION TILED SEPT. 18,1905.

Inventor Fig. 2.

Witnesses UNITED STATES PATENT OFFICE.

LEONARD WILSON, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO STANLEY G. I. ELECTRIC MFG. CO.', A CORPORATION OF MASSA- CHUSETTS.

subject of the King of Great Britain, residing at Pittsfield, county of Berkshire, State of Massachusetts, have invented certainv new and useful Im rovementsin Demand-Indicators, of whic the following is a specification.

This invention relates to an instrument for indicating the maximum demand of electric energy, and refers particularly to a maximum-demand indicator of. the Wright strip has been storing heat in t type, in which the current to be measured, or a definite portion thereof, is passed through a heating-strip arranged in close proximity to a bulb at one end of a U-sha ed tube containing a liquid and which w en heated by the current expands the air or gas in the bulb, and thus causes the liquid in the tube to overflow into a receptacle, where it indicates by the height to which it rises therein the demand on the system.

The object of my invention is to provide an instrument of this type which will not res ond to fluctuations of the current of short uration, but will only give indications of demands continuing over considerable periods. I accomplish this by separating the heating-strip and the expansion-bulb instead of winding the strip directly upon the bulb, as has been the practice heretofore, and in the space between the strip and the bulb I place a body of material having a high capacity for storing heat such, for instance,-

as cast-iron so that "the heat of the strip is not communicated immediately to the air or gas in the-eXpansion-bulb, but only after the lapse of an interval of time durin which the he body of iron. With the instrument constructed in this manner the assage of current through the heating-strip eats 1t and the expansionbulb The invention further comprises other novel features, which will be more definitely indicated in the claims appended hereto.

. The details of the construction and the method' of operation of my improved maximum-demand indicator will be better understood,by reference to the following description, taken in connection with the accompanying drawings, which illustrate the pre- Specification of Letters Patent.

Application filed September 18,1905. Serial No. TI EOH DEMAND-INDICATOR.

Patented Nov. 6, 1906.

which I Figure 1 is a front view of the indicator.

having the cover removed. Fig. 2 is an elevation of the ex ansion-bulb withthe jacket thereon, and ig. 3 is a central" section through the expansion-bulb.

Referring to the drawings, the parts of the ferred embodiment, of my invention, and in i instrument are inclosed within a casing con- 1 sisting of a back 1 and a cover (not shown in the drawings) which is hinged to the back l at the bottom and secured by a spring-catch 2 or other suitable means at the top. Ex-

tending throughopenings in the sides and secured thereto are two bindingosts 3 3, having openings therein into whic leads 4 4 may be inserted and secured by set-screws 5 5. Rotatable on these binding-posts are metallic members 6 6, to which is secured a support 7. Mounted on this su port is a U- shaped glass tube 8, filled wit liquid. At the ends of tube 8 are enlarged portions formin an expansion-bulb 9 and a compression-bu b 10, each of which is filled with air or gas. Sealed into the right-hand limb of the U-shaped tube 8 is an indicatortube 11, closed at its lower end, and mounted on the, support 7 behind this tube is a scale. 12, by which'the height of the liquid in the tube 11 can be read. The heating-strip 13 surrounds the ex ansion-bulb 9 andis connected at its en s to the metallic members; but the temperature of the air or gas in the expansion-bulb is not raised immediately, as the heat of the strip is not given off to the bulb immediately. Insteadthe heat of the strip is communicated to the iron body or jacket and stored therein, and quite a diflerence of temperature exists between the outside andinside of the jacket. However, if the same amount of current continues to flow through theheating-strip for aconsiderable period the heat-storing capacity of the 'acket will be reached, the jacket will give off heat more rapidly to the air or gas in the exa suitable i ansion-bulb, and the temperature, of the atter will be raised to a point commensurate with the quantity of the current flowing in the heating-strip. In order that the instrument may be used interchangeably on alternating-current and direct-current circuits, provide an air-gap in the iron jacket, so as to crease of the current flowing therethrough, does not immediately aflect the temperaprevent the flow of,Foucault or eddy currents therein, which would heat up the jacket, and thus impair the accuracy of the instrument when used on alternating-current circuits.

My invention therefore comprises a demand-indicator having a vessel containing a liquid, a receptacle connected thereto containing an expansible fluid which by its expansion displacesthe liquid to effect an indication, and a heating-strip for effecting the expansion of the fluid mounted in proximity to but separated from the receptacle containing the expansible fluid, so that the ill-- strument will not respond to fluctuations of the current of short duration.

My invention also comprises such a demand-indicator having a jacket of iron or other material having a high heatstoring capacity mounted between the heating stri s 6 6, which are in electrical connectionwit the binding-posts 3 3. It will be seen that when a current is passed through the strip 13 the strip will be heated by the current, and the air or gas in the bulb 9 will be heated thereby and will expand. This expension of the air or gas in bulb 9 causes the iquid in the right-hand limb of the U-shaped tube 8 to rise, and the amount of the liquid that overflows into the tube 11 is a measure of the maximum. current which has passed through the heating-strip 13.

A more detailed description of these parts of the instrument is not considered necessary, as they form no part of my invention and are well known to those skilled in the art.

Surrounding the expansion-bulb 9 is a jacket 14, made of a material having a high capacity for storing heat. I have found cast-iron best for this use, as its heat-storing capacity is very great and also as cast-iron jackets can be readily made at small cost. The jacket 14 fits down over the top of the bulb 9 and is preferably provided with cars 15, by which it is secured to the support 7-.

The heating-strip 13 encircles the jacket 14, but is insulated therefrom by a thin sheet 16 of asbestos or other suitable insulating material. Strip 13 is'held securely in position by the screws 17, which are insulated from one end of the strip by the insulatingwashers 18. With the instrument constructed in this manner a rise in the temperature of the heating-strip 13, due to an inture of the. air or gas within the expansionbulb 9 to amaterial extent, but heats up the jacket .14 and stores heat-therein. If the same current-flow continues for a considerable'pe'riod, the heat-storing capacityof thejacket will be reached and the jacket will ive-ofl heatmore rapidly to the expansionulb 9, thusraising the temperature within the'bulb and causingthe air ,or gas therein to expand and eflect the indication. For this reason momentary fluctuations of the current flowing through the heatin strip and increases in the current-flow whic continue only for a short eriod do not cause an overflow of the liqui in the U-tube 8 into the indicator-tube 11 but if the increase in the current continues for a considerable period the P113361 expansion of the air or gas in bulb 9 an the corresponding overflow of liquid into tube 11 will be obtained.

When the instrument is to beused on alternating-current circuits,- itis necessary that provision be made to prevent the circu-' lation of Foucault-or eddy currents in the jacket 14, since such currents would assist in heating'the jacket and expandingthe air or gas in bulb 9, and thus impair the accu' racy of the instrument. I have found that by slotting the jacket 14, as clearly shown in Fig. 3 the flow of eddy curr'ents in the jacket is prevented and the instrument may be used on alternating or direct current circuits interchangeably.

I do not wish to be understood as limited to the exact construction which I have shown, as modifications can be made therein which I consider within the scope of my invention and which I-aim to cover by the terms of the claims appended heretol What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. Ademand-indicator comprising avessel containing a liquid and an expansible fluid which, by its expansion, displaces said liquid to eiiect an indication, a receptacle for receiving and measuring the liquid displaced, a heating-strip mounted in proximity to but separated from said vessel, and means for connecting the heating-strip in circuit.

2. A demand-indicator comprising a vessel containing a liquid, a receptacle connected thereto containing an expansible fluid which by its expansion displaces said liquid to ef fect an indication, a vessel for receiving and measuring the liquid displaced, a heatingstrip mounted in proximity tobut separated from said receptacle, andmeans for connecting the heating-stri in circuit.

3. A demand-in 'cater comprising a vessel containing a liquid, a receptacle connected thereto containing an expansible fluid, means for trapping the li uid' displaced by the expansion of said fluid, a heating-strip mounted in proximity to said receptacle, a body of material having a high capacity for storing heat mounted in juxtaposition to said strip and receptacle, and means for connecting the stri in circuit.

4. A deman -indicator comprising a vessel containing a liquid, a receptacle connected thereto containing an expansible fluid, means for trapping the liquid displaced when said fluid expands, a heating-strip mounted in proximity to said receptacle, a body of material having a high ca acity for storing heat mounted between sai strip and receptacle, and means for connecting the strip in circuit.

5. A demand-indicator comprising a tube, a liquid contained therein, a receptacle connected thereto containing an e'xpansible fluid which by its expansion causes said li uid to overflow, a second tube connected to t e first tube to receive the liquid which overflows, an iron jacket inclosing the receptacle, a heating-strip wound on the jacket but insulated therefrom, and means for connecting the strip in circuit.

6. In a demand-indicator, a receptacle containing an exp ansible fluid, aheating-strip in proximity to the receptacle, a body of metal mounted between the receptacle and strip, said body being formed to prevent the circulation of eddy-currents therein, and

means to connect the strip in circuit.

7. In a demand-indicator, a receptacle containing an expansible fluid, aniron jacket partially inclosing the same, a heating-strip wound around but insulated from the jacket, and means to connect the strip in circuit.

In witness whereof have hereunto set. my hand this 16th day of September, 1905.

LEONARD WILSON. Witnesses:

H. HAMILTON, M. A. MOGOWAN. 

